Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 67-72)

Thesis (M.A.)--Ball State University, 2008. / Title from PDF t.p. (viewed on Sept. 09, 2009). Includes bibliographical references (p. [65]-73).

No description available.

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Thesis (M.A.)--Ohio University, March, 2005. / Includes bibliographical references (p. 73-76)

Thesis (M.A.)--Ohio University, March, 2005. / Title from PDF t.p. Includes bibliographical references (p. 73-76)

The photocyclization and photosolvolysis of a series of hydroxy-substituted biaryl methanols [special characters omitted] have been studied. The proposed mechanism involves deprotonation of the HOAr moiety and heterolytic cleavage of the C-O bond of the hydroxymethyl group [special characters omitted] in the first excited singlet state (S1), to give biaryl quinone methide intermediates, which subsequently cyclize to the corresponding chromene product and/or react with solvent to give the solvolysis product. The formation of these quinone methide intermediates is facilitated by the excited state planarization and the subsequent charge polarization (negative charge transferred from the HOAr ring into the [special characters omitted] ring) of the biaryl. Although both of these processes are influenced by steric and electronic factors, the latter turns out to have a more significant effect on reaction efficiency. When the geometry of the molecule goes from a twisted conformation to a more planar form, the molecule becomes more conjugated and thus gains delocalization energy. This energy is generally larger for the planarization in the S1 state than in the ground state. When it is large enough to overcome the steric repulsion for twisting, biaryls can planarize efficiently in the excited state, which is true for most biphenyl systems. However, it is shown that the deprotonated forms [special characters omitted] of these biaryls have an even larger driving force for S1 planarization than the neutral forms [special characters omitted]. Thus, biaryls with naphthalene ring(s) joined at the 1-position which do not planarize efficiently in the neutral form can still reach a more planar geometry after adiabatic deprotonation of the phenolic hydroxy group in S1. That is, the photocyclization of these molecules proceeds via initial adiabatic deprotonation from the twisted S1 state, followed by twisting (to the planar form) and subsequent charge polarization which expels the hydroxy group at the benzylic position [special characters omitted], to give the required quinone methide intermediate. The o,o'-biaryl quinone methides derived from the o,o'-substituted biaryl methanols are very short-lived due to rapid intramolecular ring closure and are therefore not detectable by nanosecond laser flash photolysis. The o,p’- and p,p'-biphenyl quinone methides, however, do not cyclize and as expected, are readily observable by nanosecond laser flash photolysis. When the benzylic hydroxy group is replaced by other leaving groups, the reaction can be used, in principle, as a photodeprotecting reaction and also to photogenerate acid. These and other results of the Thesis have uncovered many interesting mechanistic details of this new class of reaction and hence have increased our general knowledge of the excited state behavior of aromatic molecules. / Graduate

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Potential thermophiles for ethanol production at elevated temperature were compared based on their kinetic performances. T. thermophilus HB27 demonstrated superior kinetics and its growth was not greatly affected when containing the recombinant plasmid pTEV231. Detailed kinetic studies demonstrated that it could utilize glucose and xylose in medium containing 0.5 % (w/v) yeast extract, and could produce low levels of L-lactate, acetate and ethanol. Kinetic evaluation of the newly isolated G. thermoglucosidasius M10EXG showed it could grow on fully defined media and coferment glucose and xylose. G. thermoglucosidasius M10EXG produced higher levels of products (acetate, and L-lactate) at about 2 g/l each, compared to T. thermophilus HB27 although ethanol levels were only 0.1-0.2 g/l in shake flask fermentations under partially aerobic conditions. Improved conditions for natural transformation of T. thermophilus HB27 were determined. Optimal conditions for electroporation of were: Milli-Q water washing of cells rather than with 10% (v/v) glycerol; an electrical field of 5 kV/cm; cell concentration of 1.4x1010 cells/ml; and a DNA concentration of 500 ng in 40 Fl (125 Fg/ml) which achieved a transformation efficiency of 3x103 transformants /Fg DNA. The chloramphenicol resistance (cat) and green fluorescence protein (gfp) genes from pCJS10 were cloned into an E. coli -- T. thermophilus shuttle vector (pMK18) as possible selection markers at elevated temperatures. Both genes were expressed in E. coli DH5H and it was demonstrated that gfp expression in E. coli DH5H decreased as temperature increased to 45oC. However following transformation of T. thermophilus HB27, no evidence of expression were found. The pet operon containing adhT (with its promoter) from G.thermoglucosidasius M10EXG and pdc from Z. mobilis Zm4, was cloned into pMK18 and low level expression in E. coli JM109 occurred with some increase in ethanol production. However the pet operon was not expressed in T. thermophilus with pMK18. For further gene expression studies, a new shuttle vector, pPOPTE (4-5 kb), based on the T. thermophilus plasmid pTEV231 (containing thermostable kanamycin resistance gene) was constructed. pPOPTE was capable of multiplying in both E. coli and T. thermophilus HB27 and demonstrated higher stability and transformation efficiency compared to pMK18.